Despite its large output torque, a reluctance type motor has so various disadvantages including low rotational speed and vibration that it has scarcely been practically utilized.
A first problem to be solved in the reluctance type motor is as follows: since the magnetic path of armature coils, formed in salient poles and magnet poles, is almost closed, the inductance of the reluctance type motor is very large. This increases magnetic energy amount stored into or discharged from magnetic poles or salient poles. And also this increases the repetition frequency of such energy storage and discharge during one complete revolution of the rotor. There is, therefore, a problem that the reluctance type motor cannot rotate in a high-speed region despite of outputting large output torque. Solving the above-described problem becomes difficult with increasing output of a reluctance type motor.
A second problem is as follows: FIG. 1 shows a plan view showing a well-known three-phase half-wave current supply mode reluctance type motor. A reference numeral 16 represents a fixed armature which is made of laminated layers of silicon steel sheets. Magnetic poles 16a, 16b, --are associated with armature coils 17a-1, 17b-1, --. A rotor 1 rotates in a direction of an arrow A. A reference numeral 5 represents a rotational shaft 5. When armature coils 17b-1, 17e-1 are activated, the rotor 1 rotates in the direction of the arrow A. After 120-degree rotation, these armature coils are deactivated. Next, armature coils 17c-1, 17f-1 are activated. After 120-degree rotation, these armature coils are deactivated.
As described above, the rotor 1 rotates in the order of the armature coils 17a-1, 17d-1.fwdarw.17b-1, 17e-1.fwdarw.17c-1, 17f-1 along the arrow A. Only two salient poles contribute to generation of the above-described rotational torque, and remaining four salient poles have no relation to this generation of rotational torque. If all the six salient poles generate torque simultaneously, a generated torque will be increased three times. However, this is not attainable.
Furthermore, a third problem is as follows: when the armature coils 17a-1, 17d-1 are activated, the magnetic poles 16a, 16d are magnetically attracted radially toward the salient poles 1a, 1e. Thus, the fixed armature 16 causes deformation due to this attraction force. When the rotor rotates, the fixed armature causes deformation due to another attraction forces generated by the magnetic poles 16b, 16e and 16c, 16f and their confronting salient poles. These deformation mechanism induces the vibration of the motor. As it is technically difficult to equalize the air gap length between salient poles and magnetic poles, an attraction force received by the rotor 1 changes its direction as the rotor 1 rotates. Thus, the rotor 1 causes vibration in the radial direction. Accordingly, vibration noise is generated. And, the durability of the bearing, provided for the rotational shaft of the rotor 1, is worsened. In the case of a large-output motor, it becomes difficult to solve the above-described problems.
Furthermore, a fourth problem is as follows. When the above-described second problem is solved, it will encounter with a large ripple torque as described later with reference to FIG. 11.
Accordingly, the present invention has an object to provide a reluctance-type motor capable of suppressing vibration, rotating at high speeds, generating a large output torque and bringing flat torque characteristics.
In order to accomplish above purpose, a first aspect of the present invention provides a reluctance type motor in a three-phase full-wave reluctance type motor, comprising: n first and second salient poles having the same width, equally spaced at regular angles and disposed at both ends of an outer peripheral surface of a magnetic rotor, where n is a positive integer not less than 2; No. 1-, No. 2- and No. 3-phase armature coils wound around 6n slots, being successively offset with a phase difference of 120 degrees in terms of electric angle, the 6n slots being disposed on an inner peripheral surface of a cylindrical first fixed armature and equally spaced at regular angles; a second fixed armature identical with the first fixed armature, having slots associated with No. 1-, No. 2- and No. 3-phase armature coils which are successively offset with a phase difference of 120 degrees in terms of electric angle; means for offsetting position of the slots of the first and second fixed armatures, so that No. 1-, No. 2- and No. 3-phase armature coils are disposed with an offset electric angle of odd multiple of 30 degrees with respect to corresponding No. 1-, No. 2- and No. 3-phase armature coils, or the first and second salient poles opposing each other are disposed with a mutual offset electric angle of odd multiple of 30 degrees therebetween while the No. 1-, No. 2- and No. 3-phase armature coils and the No. 1-, No. 2- and No. 3-phase armature coils are in phase; a position detecting device for detecting rotational position of the first salient pole and generating No. 1-phase position detecting signals having 120-degree width and mutually spaced at regular angles of 240 degrees in term of electric angle, No. 2-phase position detecting signals being delayed 120 degrees in terms of electric angle from the No. 1-phase position detecting signals, and No. 3-phase position detecting signals being delayed 120 degrees in terms of electric angle from the No. 2-phase position detecting signals, and further generating No. 1-, No. 2- and No. 3-phase position detecting signals delayed from the No. 1-, No. 2- and No. 3-phase position detecting signals by an electric angle of odd multiple of 30 degrees; semiconductor switching elements connected in series with each of the No. 1-, No. 2-, No. 3-phase, No. 1-, No. 2- and No. 3-phase armature coils; a DC electric power source supplying electric power to a serial joint unit consisting of the armature coil and the semiconductor switching element; a current supply control circuit for supplying current to the No. 1-, No. 2-, No. 3-, No. 1-, No. 2- and No. 3-phase armature coils by turning on corresponding semiconductor switching elements connected in series with the No. 1-, No. 2-, No. 3-, No. 1-, No. 2- and No. 3-phase armature coils in response to the No. 1-, No. 2-, No. 3-, No. 1-, No. 2- and No. 3-phase position detecting signals by an amount of signal width of each position detecting signal; a first electric circuit for transferring magnetic energy stored in the armature coil through a diode into a small-capacitance capacitor from a connecting point of the semiconductor switching element and the armature coil and holding it to quickly reduce exciting current of the armature coil when the semiconductor switching element is turned off at a terminal end of the position detecting signal; and a second electric circuit for discharging electrostatic energy stored in the small-capacitance capacitor into an armature coil to be activated next upon activation of the next activated armature coil, when the magnetic rotor rotates a predetermined angle and the next activated armature coil is activated in response to the position detecting signal by an amount of signal width of the position detecting signal.
A second aspect of the present invention provides a reluctance type motor in a three-phase half-wave reluctance type motor, comprising: n first salient poles having the same width, equally spaced at regular angles and disposed on an outer peripheral surface of a magnetic rotor, where n is a positive integer not less than 2; 6n second salient poles having the same width, equally spaced at regular angles and disposed on an outer peripheral surface of another magnetic rotor coaxial with and rotating synchronically with the magnetic rotor; No. 1-, No. 2- and No. 3-phase armature coils wound around 6n slots, being successively offset with a phase difference of 120 degrees in terms of electric angle, the 6n slots being disposed on an inner peripheral surface of a cylindrical fixed armature and equally spaced at regular angles; at least n magnetic poles having a predetermined width, equally spaced at regular angles and protruding from an inside surface of a cylindrical magnetic member disposed in parallel with the fixed armature, the magnetic poles being wound by exciting coils; means for arranging the first and second salient poles to confront over slight air gap the inside peripheral surface of the fixed armature and the magnetic poles of the cylindrical magnetic member, respectively; a position detecting device for detecting rotational position of the first salient pole and generating No. 1-phase position detecting signals having 120-degree width and mutually spaced at regular angles of 240 degrees in term of electric angle, No. 2-phase position detecting signals being delayed 120 degrees in terms of electric angle from the No. 1-phase position detecting signals, and No. 3-phase position detecting signals being delayed 120 degrees in terms of electric angle from the No. 2-phase position detecting signals; semiconductor switching elements connected in series with each of the No. 1-, No. 2- and No. 3-phase armature coils and the exciting coils; a DC electric power source supplying electric power to a serial joint unit consisting of the armature coil, the exciting coil and the semiconductor switching element; a current supply control circuit for supplying current to the No. 1-, No. 2- and No. 3-phase armature coils by turning on corresponding semiconductor switching elements connected in series with the No. 1-, No. 2- and No. 3-phase armature coils in response to the No. 1-, No. 2- and No. 3-phase position detecting signals by an amount of signal width of each position detecting signal; a first electric circuit for supplying current to the exciting coil in response to a position detecting signal obtained through detection of the position of the second salient pole, during a period from a point where the second salient pole begins entering an opposing magnetic pole to a point where both directly confront each other; a second electric circuit for transferring magnetic energy stored in the armature coil through a diode to a small-capacitance capacitor from a connecting point of the semiconductor switching element and the armature coil and holding it to quickly reduce exciting current of the armature coil when the semiconductor switching element is turned off at a terminal end of the position detecting signal; an electric circuit for discharging electrostatic energy stored in the small-capacitance capacitor into an armature coil to be activated next upon activation of the next activated armature coil, when the magnetic rotor rotates a predetermined angle and the next activated armature coil is activated in response to the position detecting signal by an amount of signal width of the position detecting signal; a current supply control circuit for maintaining current to be supplied to the exciting coil at a value corresponding to current to be supplied to the armature coil; and means for adjusting relative position of torque generating members so that a peak of ripple torque generated by the exciting coil is overlapped with a concave portion of ripple torque of an output torque generated by the armature coil when activated.
A third aspect of the present invention provides a reluctance type motor in a two-phase full-wave reluctance type motor, comprising: n first salient poles having the same width, equally spaced at regular angles and disposed at both ends of an outer peripheral surface of a magnetic rotor, where n is a positive integer not less than 2; 4n second salient poles equally spaced at regular angles and disposed on an outer peripheral surface of another magnetic rotor coaxial with and rotating synchronically with the magnetic rotor; No. 1-, No. 2-, No. 3- and No. 4-phase armature coils wound around 4n slots, being successively offset with a phase difference of 90 degrees in terms of electric angle, the 4n slots being disposed on an inner peripheral surface of a cylindrical fixed armature and equally spaced at regular angles; at least n magnetic poles having a predetermined width, equally spaced at regular angles and protruding from an inside surface of a cylindrical magnetic member disposed in parallel with the fixed armature, the magnetic poles being wound by exciting coils; means for arranging the first and second salient poles to confront over slight air gap with the inside peripheral surface of the fixed armature and the magnetic poles of the cylindrical magnetic member, respectively; a position detecting device for detecting rotational position of the first salient pole and generating No. 1-, No. 2-, No. 3- and No. 4-phase position detecting signals having 90-degree width in terms of electric angle and continuous one another; semiconductor switching elements connected in series with each of the No. 1-, No. 2-, No. 3- and No. 4-phase armature coils and the exciting coils; a DC electric power source supplying electric power to a serial joint unit consisting of the armature coil, the exciting coil and the semiconductor switching element; a current supply control circuit for supplying current to the No. 1-, No. 2-, No. 3- and No. 4-phase armature coils by turning on corresponding semiconductor switching elements connected in series with the No. 1-, No. 2-, No. 3- and No. 4-phase armature coils in response to the No. 1-, No. 2-, No. 3- and No. 4-phase position detecting signals by an amount of signal width of each position detecting signal; a first electric circuit for supplying current to the exciting coil in response to a position detecting signal obtained through detection of the position of the second salient pole, during a period from a point where the second salient pole begins entering an opposing magnetic pole to a point where both directly confront each other; a second electric circuit for transferring magnetic energy stored in the armature coil through a diode to a small-capacitance capacitor from a connecting point of the semiconductor switching element and the armature coil and holding it to quickly reduce exciting current of the armature coil when the semiconductor switching element is turned off at a terminal end of the position detecting signal; an electric circuit for discharging electrostatic energy stored in the small-capacitance capacitor into an armature coil to be activated next upon activation of the next activated armature coil, when the magnetic rotor rotates a predetermined angle and the next activated armature coil is activated in response to the position detecting signal by an amount of signal width of the position detecting signal; a current supply control circuit for maintaining current to be supplied to the exciting coil at a value corresponding to current to be supplied to the armature coil; and means for adjusting relative position of torque generating members so that a peak of ripple torque generated by the exciting coil is overlapped with a concave portion of ripple torque of an output torque generated by the armature coil when activated.
A fourth aspect of the present invention provides a reluctance type motor in a three-phase full-wave reluctance type motor, comprising: n first and second salient poles having the same width, equally spaced at regular angles and disposed at both ends of an outer peripheral surface of a magnetic rotor, where n is a positive integer not less than 2; 3n slots equally spaced at regular angles and disposed on an inner peripheral surface of a cylindrical first fixed armature; No. 1-, No. 2- and No. 3-phase armature coils, each wound around adjacent two slots; a second fixed armature identical with the first fixed armature, having slots associated with No. 1-, No. 2- and No. 3-phase armature coils which are successively offset with a phase difference of 120 degrees in terms of electric angle; means for offsetting position of the slots of the first and second fixed armatures, so that No. 1-, No. 2- and No. 3-phase armature coils are disposed with an offset electric angle of odd multiple of 60 degrees with respect to corresponding No. 1-, No. 2- and No. 3-phase armature coils, or the first and second salient poles opposing with each other are disposed with an offset electric angle of odd multiple of 60 degrees therebetween while the No. 1-, No. 2- and No. 3-phase armature coils and the No. 1-, No. 2- and No. 3-phase armature coils are in phase; a position detecting device for detecting rotational position of the first salient pole and generating No. 1-phase position detecting signals having 120-degree width and mutually spaced at regular angles of 240 degrees in term of electric angle, No. 2-phase position detecting signals being delayed 120 degrees in terms of electric angle from the No. 1-phase position detecting signals, and No. 3-phase position detecting signals being delayed 120 degrees in terms of electric angle from the No. 2-phase position detecting signals, and further generating No. 1-, No. 2- and No. 3-phase position detecting signals delayed from the No. 1-, No. 2- and No. 3-phase position detecting signals by an electric angle of odd multiple of 60 degrees; semiconductor switching elements connected in series with each of the No. 1-, No. 2-, No. 3-phase, No. 1-, No. 2- and No. 3-phase armature coils; a DC electric power source supplying electric power to a serial joint unit consisting of the armature coil and the semiconductor switching element; a current supply control circuit for supplying current to the No. 1-, No. 2-, No. 3-, No. 1-, No. 2- and No. 3-phase armature coils by turning on corresponding semiconductor switching elements connected in series with the No. 1-, No. 2-, No. 3-, No. 1-, No. 2- and No. 3-phase armature coils in response to the No. 1-, No. 2-, No. 3-, No. 1-, No. 2- and No. 3-phase position detecting signals by an amount of signal width of each position detecting signal; a first electric circuit for transferring magnetic energy stored in the armature coil through a diode into a small-capacitance capacitor from a connecting point of the semiconductor switching element and the armature coil and holding it to quickly reduce exciting current of the armature coil when the semiconductor switching element is turned off at a terminal end of the position detecting signal; and a second electric circuit for discharging electrostatic energy stored in the small-capacitance capacitor to an armature coil to be activated next upon activation of the next activated armature coil, when the magnetic rotor rotates a predetermined angle and the next activated armature coil is activated in response to the position detecting signal by an amount of signal width of the position detecting signal.
And a fifth aspect of the present invention provides a three-phase reluctance type motor in a three-phase half-wave reluctance type motor, comprising: n first salient poles having the same width, equally spaced at regular angles and disposed on an outer peripheral surface of a magnetic rotor, where n is a positive integer not less than 2; 3n second salient poles having the same width, equally spaced at regular angles and disposed on an outer peripheral surface of another magnetic rotor coaxial with and rotating in synchronism with the magnetic rotor; 3n slots being disposed on an inner peripheral surface of a cylindrical fixed armature and equally spaced at regular angles; 3n No. 1-, No. 2- and No. 3-phase armature coils wound around adjacent two slots; at least n magnetic poles having a predetermined width, equally spaced at regular angles and protruding from an inside surface of a cylindrical magnetic member disposed in parallel with the fixed armature, the magnetic poles being wound by exciting coils; means for arranging the first and second salient poles to confront over slight air gap the inside peripheral surface of the fixed armature and the magnetic poles of the cylindrical magnetic member, respectively; a position detecting device for detecting rotational position of the first salient pole and generating No. 1-phase position detecting signals having 120-degree width and mutually spaced at regular angles of 240 degrees in term of electric angle, No. 2-phase position detecting signals being delayed 120 degrees in terms of electric angle from the No. 1-phase position detecting signals, and No. 3-phase position detecting signals being delayed 120 degrees in terms of electric angle from the No. 2-phase position detecting signals; semiconductor switching elements connected in series with each of the No. 1-, No. 2- and No. 3-phase armature coils and the exciting coils; a DC electric power source supplying electric power to a serial joint unit consisting of the armature coil, the exciting coil and the semiconductor switching element; a current supply control circuit for supplying current to the No. 1-, No. 2- and No. 3-phase armature coils by turning on corresponding semiconductor switching elements connected in series with the No. 1-, No. 2- and No. 3-phase armature coils in response to the No. 1-, No. 2- and No. 3-phase position detecting signals by an amount of signal width of each position detecting signal; a first electric circuit for supplying current to the exciting coil in response to a position detecting signal obtained through detection of the position of the second salient pole, during a period from a point where the second salient pole begins entering an opposing magnetic pole to a point where both directly confront each other; a second electric circuit for transferring magnetic energy stored in the armature coil through a diode into a small-capacitance capacitor from a connecting point of the semiconductor switching element and the armature coil and holding it to quickly reduce exciting current of the armature coil when the semiconductor switching element is turned off at a terminal end of the position detecting signal; an electric circuit for discharging electrostatic energy stored in the small-capacitance capacitor to an armature coil to be activated next upon activation of the next activated armature coil, when the magnetic rotor rotates a predetermined angle and the next activated armature coil is activated in response to the position detecting signal by an amount of signal width of the position detecting signal; a current supply control circuit for maintaining current to be supplied to the exciting coil at a value corresponding to current to be supplied to the armature coil; and means for adjusting mutual position of torque generating members so that a peak of ripple torque generated by the exciting coil is overlapped with a bottom portion of ripple torque of an output torque generated by the armature coil when activated.
In accordance with the present invention, the reluctance type motor has a large inductance since the magnetic core of the armature and the salient poles of the rotor interact to close their magnetic path when the armature coil is activated. Hence, current of the armature coil builds up slowly in the beginning, while decrease of the current is delayed when the armature coil is deactivated. Accordingly, there is a disadvantage that the motor cannot run fast. This disadvantage is enhanced when the output of the motor is large.
According to the present invention, when the armature coil is deactivated, magnetic energy stored in the armature coil is discharged into a small-capacitance capacitor to charge it up and make current reduce steeply. Furthermore, high voltage of this capacitor is utilized to sharply build up current supplied to a next activated armature coil. Therefore, even if a motor has a large output, it can rotate at a high speed.
Next, as all the salient poles of the rotor always contribute to generate output torque, the output obtained becomes large.
Furthermore, as all the salient poles of the rotor are magnetically attracted radially outward, generation of vibration is suppressed.
If the motor is constituted so as to accomplish the above-described second function, the following disadvantage will arise: as later described with reference to FIG. 11, a large ripple torque is generated corresponding to the width of the magnetic poles. The present invention provides a device which generates another ripple torque having a peak overlapped with the bottom of the ripple torque to flatten the overall output torque, thereby eliminating the above-described disadvantage.
As explained above, the present invention brings a large output torque approximately 10 times as much as that of the same type induction motor. The rotational speed can be increased up to 20 thousands rpm as occasion demands. Compared with a conventional reluctance type motor shown in FIG. 1, vibration is reduced and rotation of the motor is smoothed.
Furthermore, the output torque characteristics is flattened.